Weather Service Report

FXUS66 KPQR 241614

Area Forecast Discussion...corrected 
National Weather Service Portland OR 
910 AM PDT Mon Apr 24 2017

.SYNOPSIS...Expect periods of rain through midweek with decreasing
showers Thursday and Friday. Drier weather looks to return Saturday,
but is looking short lived with additional wet weather possible
Sunday and Monday.  


.SHORT TERM...Today through Thursday...Water vapor satellite imagery
reveals an upper level trough sagging southeastward across the
Pacific Northwest. A pocket of -28 to -30C 500mb temperatures is
currently off the Washington coast and will drop southeastward across
the area this afternoon. Closer to the ground, a surface low 
pressure is currently moving onto the Oregon coast and will push 
eastward towards the PDX metro and Columbia River Gorge today.
The net effect will be the widespread rain and mountain snow this 
morning transitioning to a showery pattern this afternoon. Will 
leave a thunder mention out of the forecast for now as it looks 
marginal this afternoon, but will monitor trends and update the 
forecast accordingly if it looks like we will get sufficient surface 
heating. In addition, areas to the south of the low pressure track 
will see gusty southerly winds increase later this morning and early 
this afternoon...likely into the 25-35 mph range for a couple hours.

Shortwave ridging building into the Pacific Northwest should bring a
fairly quick decrease in showers tonight. However, the next occluding
frontal storm system will push more rain towards the area Tuesday.
The 12z GFS sped up precipitation timing closer to the 00z EC
solution and suspect most of the region will be wet by at least late
Tuesday afternoon...if not sooner. A 150-160kt jet will then take aim
at Oregon Tuesday night with our CWA generally on the polar side of
the jet through Thursday. This should produce plenty of showers with 
lowering snow levels across the Cascades. Additional Winter Wx 
highlights for the Cascades look possible. /Neuman 

.LONG TERM...No Changes. Previous discussion follows...Wednesday
night through Sunday...Showers will continue across the forecast area
Wednesday night into Friday as a couple of more disturbances ride
through on a jet stream that turns more northwesterly through through
Friday. The models are now in better agreement that enough of an
upper ridge will build early in the weekend for some drying. The next
system is expected about Sunday. Tolleson


.AVIATION...Surface low moving onshore around KTMK has weakened
somewhat. However, still expect probable gusts 20-25 kt south of
a KTMK to KUAO line through roughly 23z. Coastal areas are 
expected to remain predominantly MVFR in cigs and vis with 
pockets of IFR Vsbys as the low moves ashore. Most guidance 
holds MVFR at the coast through at least 06Z Tue, but there is 
some chances for improvement after that. Inland, MVFR Cigs and 
Vsbys have become more dominant and should last through 22-00Z 
with trends toward VFR after that. Precipitation becomes showers 
after midday as the low/front shifts east of the area. Could then
see some heavier showers and cumulus buildups for the remainder
of daylight hours today as the lower level instability could 
favor fairly deep cell growth. Showers quickly taper off later
this evening. Forecast guidance has coastal terminals remaining
MVFR through the night with inland terminals picking up an MVFR
Cig 020-030 after 25/12z and lasting until at least 25/18z.

KPDX AND APPROACHES...MVFR conditions primarily from cigs around
025 and occasional Vsbys are expected through midday. Cigs 
should then begin to break and lift, however, heavier showers 
could briefly bring MVFR cigs and vis this afternoon into early 
evening. /JBonk


.MARINE...Surface low has moved onshore in the general vicinity f
Tillamook during the past hour. Have already begun to see wind 
shifts to the west south of the low. Areas north of the low will
see a more dramatic wind shift from south to southeast to 
northwest by afternoon. Lower end SCA wind gusts 20-25 kt will 
continue this afternoon. A minor dynamic fetch has brought seas 
10-12 ft mainly south of the low as well. Should see the seas 
subside shortly after the winds diminish this afternoon. 

Active weather pattern continues as there is another system on 
Tuesday that will likely bring high-end small craft advisory wind
and possibly brief low-end gales. Seas look to remain around 7 
to 9 ft. Surface high pressure then begins to build offshore
shunting the surface lows mainly north of the waters and keeping
a relative lull in winds through Friday. Seas next reach 10-11 
ft Thursday through early Friday as the southern end of a swell 
train clips the northern waters from a surface low crossing the 
Alaskan Panhandle. /JBonk


OR...Winter Weather Advisory until 8 PM PDT this evening for 
     Cascades in Lane County-Northern Oregon Cascades.

WA...Winter Weather Advisory until 8 PM PDT this evening for South 
     Washington Cascades.

PZ...Small Craft Advisory for winds until 2 PM PDT this afternoon 
     for Coastal Waters from Cape Shoalwater WA to Cascade Head 
     OR out 60 nm.

     Small Craft Advisory for winds until 4 PM PDT this afternoon 
     for Coastal Waters from Cascade Head OR to Florence OR out 
     60 nm.

     Small Craft Advisory for hazardous seas until 5 PM PDT this 
     afternoon for Coastal Waters from Cascade Head OR to 
     Florence OR out 60 nm.

     Small Craft Advisory for Rough Columbia River Bar from 2 PM 
     this afternoon to 6 PM PDT this evening.

     Small Craft Advisory for Rough Columbia River Bar from 3 AM to 
     7 AM PDT Tuesday.



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This discussion is for Northwest Oregon and Southwest Washington
from the Cascade crest to 60 nautical miles offshore. The area is
commonly referred to as the forecast area.

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